No not simple. After the merger the company did a huge international expansion, international flights require more crew members, it's not attrition that has driven the east movement. After the merger operating costs went way up (east costs about twice of awa) making west flying unprofitable. During fuel crisis company shrunk west 10% because of this new higher cost. Fact 1/3 of e-190 seats belong west, same for ata 757. Fact awa work rules applied east would require 400 new pilots east, fact 27 out of 30 contract sections were finished 4 years ago.Simple.